Bridging of large bone defects such as those which occur as a result of traumatic extrusion, radial tumor resection and massive sequestration due to infection is one of the most challenging orthopedic problems. Fresh autogenous bone is regarded as the best grafting material. However, there are cases in which sufficient quantities of autogenous bone are not available or the secondary surgery to obtain bone is too severe and traumatic.
The use of exogenous material may decrease the need for secondary surgery to obtain suitable graft material. Furthermore, failure of bone autografts is between 13-30% and is even higher when allogenic frozen or freeze-dried bone is used. Clearly then, there is a need for a suitable graft material that can be used in repair of bone defects including those secondary to tumor, trauma, and osteomyelitis.
Several attempts to use exogeneous bone graft material have been tried with varying degrees of success. Basically two approaches have been taken: osteoinduction and osteoinvasion. The main difference between these methods is the mode of host bone ingrowth. Osteoinductive bone grafts rely on the bone graft to induce osteogenic precursor cells in marrow and connective tissues surrounding the graft to dedifferentiate and give rise to new bone formations. Osteoinvasive bone grafts rely on host cells migrating into the graft and producing new bone formations.
Of the two processes, the osteoinductive grafts have been more successful than the osteoinvasive grafts. Typically the osteoinductive grafts have been incorporated into the host bone within a 2-6 week period, whereas osteoinvasive grafts have been found to be non-incorporated as long as 1 year from implantation.